This invention relates generally to antennas for the transmission and reception of radio frequency (RF) energy, and more particularly to methods and apparatus providing high isolation between transmitting/receiving elements of multiple element antenna arrays.
Multiple in, multiple out (MIMO) antenna system are sometimes used in wireless computer networks such as local area networks (LANs) or WI-FI service. A MIMO antenna system combines the antennas by controlling phase differences and/or amplitude or gain differences between the antennas. This combination is used to form different beam shapes to eliminate interference and/or to enhance a signal in a selected direction. Thus, a MIMO antenna system is, to some degree, similar to an adaptive array.
The antenna transmitting/receiving elements used in a MIMO array may inherently have 15 DB of isolation. Any combination of the transmitting/receiving elements can be used for receiving or transmitting. However, antenna transmitting/receiving elements having only 15 dB of isolation may not achieve the most effective beam steering or adaptive steering, especially with elements having the same individual directional pattern.